Claude Opus 4.5 and Sonnet 4.5 removed from /model selection, require launch flag

Anthropic has removed Claude Opus 4.5 and Sonnet 4.5 from the interactive /model selection menu within active sessions. This change affects users who previously could switch between models mid-session, particularly when managing token usage near context limits.

What changed

The /model command no longer lists Opus 4.5 or Sonnet 4.5 as available options during an ongoing session. Users discovered this when attempting to switch to less token-intensive models when approaching session context limits.

How to access older models

To use Opus 4.5 or Sonnet 4.5, you must now start a new session with the --model flag and specify the full model ID:

claude --model claude-opus-4-5-20250514
claude --model claude-sonnet-4-5-20250514

The model ID format follows the pattern: claude-{family}-{version}-{date}. These older model IDs are not included in the /model picker interface and must be specified directly at session launch.

Practical implications

This change means you can't switch to these older models within an existing session. If you prefer using Opus 4.5 or Sonnet 4.5, you need to start fresh sessions with the appropriate flag. This affects workflow for users who regularly adjust model selection based on token consumption or specific task requirements.